Current building practices in North America and elsewhere utilize pre-cast concrete wall panels to form the perimeter walls of a building. A plurality of concrete inserts are embedded in the concrete panels when they are pre-cast, such that a substantially flat elongate center portion of each concrete insert is located flush with the intended inside surface of the pre-cast concrete wall panels. An access slot through the elongate center portion of each concrete insert provides access for an attaching bolt to connect with a captive nut, located in an enclosed concrete free channel under the elongate center portion, the enclosed channel commonly referred to as a “nut box”. The nut is selectively positioned under the access slot to receive the inserted attaching bolt. An attaching bolt is typically first inserted through an aperture in a structural member of the building and then secured to the captive nut in the nut box of the concrete insert pre-cast in the concrete wall panel, thus securing the pre-cast concrete wall panel to the structural member of the building, to form the perimeter walls of the building.
Concrete inserts typically have a metal, housing formed from a single sheet of plate steel, being bent into an inverted “U” shaped or “V” shaped channel with an open bottom and open ends. The elongate center portion forms the valley of the inverted “U” or “V” shaped channel and opposing longitudinal sides depending from the elongate center portion form the sides of the inverted “U” or “V” shaped channel. The inverted “U” or “V” shaped channel of the nut box only allows the nut to be displaced longitudinally under the open slot in the nut box, and prevents the nut from rotating when an attaching bolt is threaded into the nut. Typically the nut is biased against the bottom of the elongate center portion by a spring compressed between the nut and the bottom wall of a not box insert which covers the open bottom and open sides of the housing, the nut box insert and the housing together forming the not box for keeping wet concrete out of the nut box during the forming process. Although it is been attempted to construct a nut box insert for sealing the bottom and ends of the housing solely with Styrofoam™ foam and dispensing with the spring, due to its lower cost and simplicity, this arrangement does not exert sufficient pressure against the nut to keep it in a preselected position while the concrete panel is attached to a building. Further, such foam is nut box inserts may be deformed or displaced during the forming process potentially allowing wet concrete into the nut box and preventing the nut from, traveling along the nut box under the slot in the elongate center portion thus preventing adjustability of the concrete insert.
Accordingly, there exists a need for a concrete insert with a foam nut box insert which sufficiently biases the nut under the nut access slot against the elongate center portion of the concrete insert and resists deformation or displacement during the concrete panel forming process.